Major progress during the last twelve months has been in the amino acid sequence analysis of the anti-arsonate hybridomas that have been generated in A/J mice. The primary structural analysis has revealed an unexpected degree of heterogeneity and the relationship between these structures and idiotypy are under current investigation. During the last twelve months, twelve different publications have resulted from these kinds of studies, all published in referred journals. More recently, we have utilized funds from this grant to establish T cell hybrids in the arsonate system, and while separate funding for this project has just been requested, it was under the auspices of this grant and the projects derived therein that this important piece of work was initiated. In addition to the above, this grant has supported primary structural analysis of human immunoglobulin variable regions and three papers have been submitted for publication concerning the relationship of the cross-idiotypic specificity among the mixed cryoglobulins and their primary structure.